This invention relates to a group of compounds generally referred to as phenethanolamines. The compounds provided are unique since they are effective in the treatment of obesity yet are essentially devoid of cardiac effects.
Some of the most extensive efforts in basic research have been in the area of .beta.-phenylethylamine derivatives, many of which are catecholamines. A great deal of study, for example, has been carried out on the naturally occurring catecholamine epinephrine. Epinephrine is a potent sympathomimetic drug and a powerful cardiac stimulant. The use of epinephrine is limited, however, due to its undesirable side effects, which include fear, anxiety, tremor, tenseness, throbbing headache, increased blood pressure, dizziness, respiratory difficulty and palpitation, as well as its short duration of action.
The use of drugs which cause more than one biological effect can be very dangerous for the biological system. For example, since both bronchodilation and cardiac stimulation are mediated by the broad group of receptors known as .beta.-receptors, a drug acting on such .beta.-receptors not only would effect bronchodilation, but additionally could cause observable effects upon the heart. In fact, some individuals allegedly have died from ventricular fibrillation caused by excessive .beta.-stimulation after using bronchodilation agents; (See Greenburg and Pines, Br. Med. J. 1, 563(1967).
Since .beta.-phenethylamine type compounds are known to have a variety of pharmacological activities, considerable research has been devoted to achieving a separation of the various biological effects of such agents. It now has been found that by selecting a unique group of N-phenylpropyl phenethanolamines, and by separating the optical isomers of certain of such compounds, a unique and unexpected degree of lipolytic activity with little or no cardiac stimulatory activity surprisingly is achieved. The discovery of compounds having a separation of cardiac activity from lipolytic activity permits the chronic administration of such lipolytic agents to obese animals so that weight control is effected by loss of adipose tissue, or prevention of the formation thereof, without accompanying adverse cardiac effects.